Do I need a cam??

[shiftdtlb42]

So I have a 2007 Silverado vortec max with 105k miles. I had a misfire code last week and it was the intake valve lifter on cylinder 4. I replaced all the lifters and guides with the DOD delete kit from Briantooley. My lifter roller and cam all looked in good shape but lifter wasn't working correctly. Now that's it's all back together I have a rough idle and the misfire I have is from cylinder 4. No other cylinders are missing. I have new plugs wires and coil pack. I have tried everything. All my cylinders are reading 90 PSI on compression except cylinder 4, it's reading 60... what to do now? Do I need a new cam or do I need to have my valves checked? I am out of ideas, thanks in advance!!

[newdude]

Compression seems low across the board? Were you able to see the cam lobes when you did the lifters?

[Podor]

You need a cam. If the roller is scored at all, it causes damage to the cam. I also thought that the cam grind on the DOD cylinders was different to compensate for the lifters, so if you install normal lifters you won't get the proper lift.

[shiftdtlb42]

I looked at the lobes and they looked good, I caught the lifter just in time before it messed up the roller and cam, if I needed a cam wouldn't I have a misfire on all the cylinders part of the DOD? I thought the compression was low on the cylinders as well. But runs great except for cylinder 4.

[shiftdtlb42]

I am currently driving it and my oil temp is aroumd 235.. is that fine? Seems kinda high. I run 5w 30 syn.

[Podor]

I did a bunch of research when I had a G8 about DOD/AMF deletes. The cam grind is different from AMF and non AMF cylinders to compensate for the differences. Most delete kits don't have a cam because guys usually choose an aftermarket cam. I highly recommend swapping the cam. Just because you are only seeing one misfire doesn't mean the cam grind is right for the change. The new push rod length may be different and not compatible with the old cam. Cylinder pressure should be at least 120 psi. The 30% difference is alarming as well. Long story short, change the cam.

[shiftdtlb42]

Ok.... tomorrow I'm going to do a leak down to see... I just don't wanna do a complete top end rebuild and still have a misfire because my rings are bad on that cylinder or something. What cam would you recommend? I want something will a little more torque for towing but nothing crazy. I don't want to have to put torque converter and stuff.

[shiftdtlb42]

Also I can't figure out if my truck is vvt or not... I can't see the cover without taking everything off

[Podor]

I'm 80% sure you don't have VVT. I can feel the front cover behind the water pump from the top on my wife's 07 5.3. The cover is flat underneath the pump, no VVT. If it jets out where the cam gear is, it has VVT.

 

I hear ya about verification. There's nothing like doing a bunch of work only to find out you have other issues. The good thing is you did the hard work with the lifters. The cam can come out with the lifters in and the heads on.

 

There are so many cams, I wouldn't know where to start.

[shiftdtlb42]

Really??? How would I be able to get the cam out without the lifters falling in the block?

[Chris]

There are dowel pin holes in the block. You spin the cam while inserting them. There is a GM part, but I think the diameter is 5/16

[shiftdtlb42]

Wow I never knew that! That will take a lot less stress out on me about it. But doing all the research on cams is really driving me crazy. As far as rebuilding a motor, pretty easy to me, but when I get to cams im completely lost. Im going to put long tube headers and a full exhaust in the future but I still dont know about which cam. I cant even find a stock cam. All I see are numbers and nothing says if i need longer pushrods or anything

[Podor]

The good thing about an Ls is you can throw just about any cam at it and make more power. Gen 1 and 2 required more thought and planning. The main things to keep in mind are how much lift and valve overlap. Ls motors can take quite a bit of lift, but it requires springs/push rods/adjustable rockers if you get too big. Overlap, how long the valves stay open at the same time (caused by lobe separation and duration), can effect normal driveability. A cam with a lot over overlap sounds cool, but it won't make a lot of vacuum for your power booster and will run pretty rough at idle.

 

Here's a good article.

http://www.lsxmag.com/tech-stories/engine/understanding-ls-valvetrain-upgrades/

[Podor]

I think you have a L76, which is the same as the Trailblazer and G8. Do you remember if you had the cathedral intake ports or rectangular ports?

[shiftdtlb42]

Yea my rpo code says l76 and they were rectangle ports.